Today's gathering of financier George Soros, Walmart chief executive Robson Walton, World Bank president Robert Zoellick, Norway's prime minister Jens Stoltenberg, and others was designed to demonstrate corporate approval for efforts to prevent deforestation in countries such as Brazil, Indonesia, Papua New Guinea and Guyana.

There was intense speculation today about new funding. Mexico is also expected to make an announcement, and there are indications Walmart is nearing a more sustainable policy of sourcing materials.

Negotiations are the most promising aspect of the summit so far. The UN secretary general Ban Ki-Moon who is due to attend the event, said on his arrival on Tuesday that conditions were "ripe" for a deal. Destruction of forests for sprawling cattle ranches or vast soya bean and palm oil plantations is responsible for 15% of global greenhouse gas emissions.

Campaigners nearly reached a deal on forests at the Copenhagen climate summit last year. Led by Norway and America, the international community has pledged $4.5bn for forest protection. A number of corporates are also interested in forest protection – to gild their image, or in anticipation of using them to offset their own greenhouse gas emissions.

But prospects for a deal at Cancun are hostage to the American all-or-nothing negotiating position. The US envoy, Todd Stern, has said repeatedly he will not sign on to a deal on deforestation or other issues unless he sees progress on the core US demand of transparency. Bolivia also has strong objections to creating a market system around forests.